Catalytic Curtius Rearrangement And Chan-Lam Coupling Using Azides As Nitrogen Source

Nitrogen-containing organic compounds are closely associated with life science,materials and human health,thus the construction of C–N bond is of great significance in organic chemistry.For a long time,chemists have been devoted to the exploration of efficient and practical amination reactions thus the development of clean and efficient oraganic azides is one of the important directions in this erea.Organic azides mainly have the following advantages as a nitrogen source:1)Organic azides are easy to prepare and use;2)Nitrogen is the only by-product in the reaction involving organic azides,which conforms to atomic economy and the idea of green chemistry.3)The N–N₂bond can be used as internal oxidant to promote the formation of high-priced metal complexes in situ,which can avoid the addition of external oxidant.4)Organic azides can be used as synthetic precursors and protective groups for primary amines5)What’more,due to the development of Click chemistry,the reaction involving organic azides has excellent functional group tolerance and good biocompatibility.1.DMAP and copper co-catalyzed Curtius rearrangement reaction.When heated,acyl azides will release nitrogen and rearrange to form isocyanates,which can be further converted to amines derivatives.The reaction is named Curtius rearrangement and widely used in organic synthesis.In this paper,we reported the Curtius rearrangement catalyzed by DMAP and copper,which has the following advantages:1)Reacting under mild redox neutral reaction conditions.2)Using cheap DMAP and copper as catalysts with as low as 0.1 mol%loading.3)High atom efficiency,with N₂ and CO₂ as the only by-products.4)Wide substrates scope and working well with a wide range of organic carboxylic acids including alkyl,alkenyl and aryl carboxylic acids.5)High efficiency with a 87%average yield for all 84 examples.6)The reaction is stereospecofic,and leads to the enantionmeric excesses value up to 99%.The catalyzed Curtius rearrangement can be used to construction amine derivatives in one-pot,which has great potenitial in chemical industry,pharmaceutical chemistry and natural product synthesis.2.Visible light and metal co-catalyzed Chan-Lam cross-coupling reaction.Oxidative cross coupling reaction of phenylboric acid with nucleophile under metal catalysis is named Chan-Lam（Chan-Evans-Lam）cross-coupling reaction.Based on previous research on amination reaction,and inspired by the cooperative catalytic reaction between visible light and metals,we developed the catalyzed Chan-Lam cross-coupling to build aromatic amines efficiently,which using phenylboric acid as coupling reagent and organic azides as nitrogen source.The protocol has good functional group tolerance and is suitable for large steric hindrance azides,which provides a new method for the synthesis of various aromatic amines.Moreover,it is suitable for drug-derived phenylboric acid and aryl azide,that has potential application in organic synthesis and drug molecular modification.